ImmuNext has identified and developed a putative lead anti-VISTA monoclonal antibody (mAb) that we aim to bring to the clinic for the treatment of human autoimmune disease. VISTA is a member of the highly successful negative checkpoint regulator (NCR) family of drug targets, whose members have demonstrated proven efficacy in inducing long-term remissions in human cancers. We contend that antibodies that suppress immune function by enhancing VISTA's function will prove effective in a broad array of human autoimmune diseases. The unique nature of VISTA to regulate both lymphoid and myeloid cells suggests that its modulation will be best suited toward the treatment of SLE, where defects in both subsets have been identified. With a strong patent position, state-of-the-art approaches and a skilled, experienced drug development team, we will develop a first-in-class NCR-targeted therapeutic for the treatment of autoimmune disease. In Phase 1 we will identify a cynomolgus cross-reactive lead and a backup mAb through functional screening of an anti-VISTA human antibody library. We currently have a human CD3-activated T call assay for our primary screen. Our choice of the best functional antibody and a backup will come from: 1) using in vitro assays, 2) by confirming activity using a human-VISTA knock-in (hV-KI) mouse strain and 3) with two models of autoimmune inflammation, concanavalin A induced hepatitis and, following selection, a graft vs. host disease model. After selection of the best antibody and a backup, we will advance into Phase 2 with lead optimization and pre- clinical development. The constant region of the lead antibody will be engineered through Ig isotype and FcRn engineering, and we will choose the best one to develop as the final lead molecule. This lead will be assessed for immunogenicity and manufacturing liabilities, and will be used to study the mechanism of action (MOA) in hV-KI mice. Additionally, we will examine the potential for this new therapeutic to induce immunological tolerance using transplant models. PK/PD relationships will be measured and rodent toxicity investigated. We will also develop PD biomarkers to inform future clinical plans using a variety of approaches, including examining tissues and cells by Phosflow and RNA-seq in drug-treated settings. By examining VISTA and the lead MOA in SLE human patient samples compared to healthy controls, we will potentially identify VISTA biomarkers for future clinical trials. With a qualified lead in hand, we will commence cell line development and non-GLP PK/PD and toxicological assessment in cynomolgus non-human primates. We have convened a panel of experts that will help collect, analyze and process the data generated from these studies to outline a clinical strategy and an IND-enabling GLP tox study. The first-in-class anti-VISTA mAb will ultimately provide patients with a unique checkpoint regulator drug to not only treat their symptoms, but also to provide them the opportunity to reset their immune system back to a healthy homeostatic state.